From: "Russell Jocoy" 
To: ea8yu{at}arrl.net, atm{at}shore.net
Reply-To: "Russell Jocoy" 


>From: Goran Hosinsky 
>Reply-To: Goran Hosinsky 
>To: atm{at}shore.net
>Subject: ATM ROC control
>Date: Fri, 25 Jul 2003 13:15:22 +0100
>
>
>I am doing a 10” f8 mirror with a tile as a tool. The tile is 8.7” in
>diameter.
>The ROC was becomming a bit short, so the last two hours I have been
>working TOT with center over center stroke, overhang 1.5 “- 2” at each
>end, #320 grit. The ROC has varied about 1” back and forth, which probably
>is the measuring tolerance using a flashlight at the side of the eye to
>find the
>center of curvature. I do not see the ROC getting longer. What am I doing
>wrong?
>Goran
>
>
>


("atm{at}shore.net")

     Goran,    my friend, stop worrying about the depth and your "f-number"
at this point and create a
sphere on the surface. You will be close to the depth you desire. If your
"f-number" is all that important
to your process will be concentrated on this and not the figure of your
glass. I was shooting for an f-5
and ended up with 4.7, this is not a big deal. The big deal is the surface
of your mirror and how well
it is figured.  Concentrate on making a telescope mirror "not"
and F number. ..That "F" number will show
it's face to you when you start testing your mirror. Unless you are under
contract to produce a specific
"f" number for  commercial purposes ,... Relax and grind to the
song of the sphere.  The number will
come up at the end and will be close to what you want.... Again, don't
concentrate on numbers at
this time, concentrate on grinding a surface that can be figured into the
numbers you want. If they don't
hit the mark dead nuts, you can still be happy with the number you end up with.
                  Of course you can always go back to 220 and grind out the
polished surface to get ...   .2 "f"
numbers off the surface, but if you do.. you need to also replace the
piston rings in your automobile
because the contact is not as close to the cylinder wall as you want it.
Ease up man, Grind, and polish,
grind and polish,.. Look at the surface, polish.., figure.... figure,...
test,.. test,... test,  figure,.. test...
                                      Sorry I am rambling again... Russ J.

("atm{at}shore.net")

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